J Sports Sci Med. 2008 Mar 1;7(1):60-6. eCollection 2008.
The purpose of this study was to determine the effect of drafting distance on the drag coefficient in swimming. A k-epsilon turbulent model was implemented in the commercial code Fluent(®) and applied to the fluid flow around two swimmers in a drafting situation. Numerical simulations were conducted for various distances between swimmers (0.5-8.0 m) and swimming velocities (1.6-2.0 m.s(-1)). Drag coefficient (Cd) was computed for each one of the distances and velocities. We found that the drag coefficient of the leading swimmer decreased as the flow velocity increased. The relative drag coefficient of the back swimmer was lower (about 56% of the leading swimmer) for the smallest inter-swimmer distance (0.5 m). This value increased progressively until the distance between swimmers reached 6.0 m, where the relative drag coefficient of the back swimmer was about 84% of the leading swimmer. The results indicated that the Cd of the back swimmer was equal to that of the leading swimmer at distances ranging from 6.45 to 8. 90 m. We conclude that these distances allow the swimmers to be in the same hydrodynamic conditions during training and competitions. Key pointsThe drag coefficient of the leading swimmer decreased as the flow velocity increased.The relative drag coefficient of the back swimmer was least (about 56% of the leading swimmer) for the smallest inter-swimmer distance (0.5 m).The drag coefficient values of both swimmers in drafting were equal to distances ranging between 6.45 m and 8.90 m, considering the different flow velocities.The numerical simulation techniques could be a good approach to enable the analysis of the fluid forces around objects in water, as it happens in swimming.
本研究旨在确定划水距离对游泳中阻力系数的影响。在商业代码 Fluent(®)中实现了 k-epsilon 湍流模型，并将其应用于划水情况下两个游泳者周围的流体流动。针对游泳者之间的不同距离（0.5-8.0 m）和游泳速度（1.6-2.0 m.s(-1)）进行了数值模拟。为每个距离和速度计算了阻力系数（Cd）。我们发现，随着流速的增加，领先游泳者的阻力系数减小。对于最小的游泳者之间的距离（0.5 m），后面游泳者的相对阻力系数较低（约为领先游泳者的 56%）。这个值逐渐增加，直到游泳者之间的距离达到 6.0 m，此时后面游泳者的相对阻力系数约为领先游泳者的 84%。结果表明，后面游泳者的 Cd 在 6.45 到 8.90 m 的距离范围内与领先游泳者相等。我们得出结论，这些距离允许游泳者在训练和比赛中处于相同的流体动力条件下。要点领先游泳者的阻力系数随着流速的增加而减小。最小的游泳者之间的距离（0.5 m）时，后面游泳者的相对阻力系数最小（约为领先游泳者的 56%）。考虑到不同的流速，在划水时，两个游泳者的阻力系数值在 6.45 m 和 8.90 m 之间相等。数值模拟技术可以很好地分析水中物体周围的流体力，就像游泳中一样。
